This invention relates generally to the field of commercial timers and more particularly to providing a timer and indexing mechanism for presetting the duration of a timed period of operation.
In previously known timer mechanisms which have been operable for controlling a commercial coin operated machine, such as an automatic fabric drying machine, it has been common practice for the coin slide actuator to rotate the timer shaft through a predetermined angle in a direction opposite to the timing rotation for presetting a period of time corresponding to each coin slide insertion. These previous timers have generally included ratchet or cam mechanisms for rotating the shaft through this predetermined angle. Multiple coin slide insertions have been used in many instances to accumulate a desired quantity of operating time.
In U.S. Pat. No. 3,056,307 the timer shaft includes a lever-mounted arcuate cam surface which is engageable with a roller on the coin slide actuator. As the slide is advanced, the roller contacts the arcuate cam surface and rotates the timer shaft toward the start position.
In U.S. Pat. Nos. 3,090,843 and 3,237,466 examples of time accumulating shaft indexing devices which include ratchet mechanisms actuated directly by a coin slide are shown.
In U.S. Pat. Nos. 3,462,565 and 3,462,566 and the coin slide actuator axially moves the timer shaft and closes the timer contact to initiate the cycle of operations. At the end of the cycle of operations the timer shaft is cammed outwardly to open the timer contact and terminate the cycle.
In U.S. Pat. Nos. 3,576,137 and 4,023,419 the indexing mechanisms include rack and gear arrangements. The mechanism is clutched so that shaft rotation occurs during the withdrawal of the coin slide.
A common problem of most of these prior art timer mechanisms has been the inaccuracy in the angular movement of the setting mechanism and thus also in the timed length of cycle. A cycle which runs longer than the desired period of time can significantly increase the operating cost to a laundry owner. Also, a cycle which is consistently shorter than the desired period of time will result in wet fabrics and a dissatisfied customer.